iPhone 5 camera issue

Hi

I have issue with my iPhone 5's camera. Here's a photo to illustrate it


You can see in the lower third of the photo there is a mark, this is showing on every photo I take. Anyone know what's causing this? My phone is obviously still under warranty, do you think Apple would replace/fix it?

Thanks

 

Ok, I'll take it in to my local store when I have the chance. Thanks a lot for your response. I wonder if this is a design issue, or just bad luck? Did they say what had caused it?